HISTORIC SHORELINE CHANGE ALONG THE LAKE ONTARIO COAST IN NIAGARA AND ORLEANS COUNTIES, NEW YORK

Record-high water levels in 2017 and 2019 with associated coastal flooding along the Lake Ontario coast have awakened many to the effects of increasing precipitation in the Great Lakes watershed. In New York, widespread erosion led to extensive engineering interventions, including dumping of large rip-rap onto the base of coastal bluffs. But is this coastal erosion truly unusual? Have coastal erosion rates been increasing in recent decades? To address these questions, we compute long- and short-term coastal erosion (and accretion) rates in a GIS environment using georeferenced aerial photographs and other imagery from 1875 to present. The study area encompasses the shoreline of Niagara and Orleans counties, and we analyze changes in shoreline position in a GIS environment across transects every 50 m along the coast. Our initial results indicate that average erosion rates on individual transects range from <0.1 to more than 1 m/yr and accretion rates are observed at <0.1 m/yr. Specific periods of time (e.g. 1951-1964) yield a greater distribution of rates. The greatest erosional rate observed at a single transect was between 2005 and 2011 at 3.4 m/yr and the greatest accretional rate was observed between 2014 and 2017 at 1.25 m/yr. Such examination of interval rates suggests there has been no systematic increase in rates of coastal recession in recent decades. Some portions of the study area show accelerated erosion in the last decade, whereas others show highest recession rates in the late 20^th century. This analysis of coastal changes in Niagara and Orleans counties will provide a framework for local officials to better understand the changes that have occurred during the recent high-water events and the extent to which these recent events characterize a long-term change in coastal erosion.